This same thing just happened to me today.
I was on the phone with 4 different support people at U.S. Cellular -- same issue with my HTC Desire. They said the only way to fix it at this time was to do a full phone reset, which I refused to do (since I just updated to Froyo 2.2 a few days ago and had to re-log everything - I'm NOT doing all that again!).
They said it's a app problem, and they are working on putting in a trouble ticket with the app developer and would call me when a solution occurs (yea, like I believe that one!).
So after 3 hours of calling back & forth and being transferred and dropped, the solution is ZERO (other than to tell me to go into the store and see if they can manually do something).
On another note - my battery is losing power like crazy - and this just started today as well. Was only talking on the phone - not using apps - and it's nearly drained. So there is more going on than just the weather and date!